package src.com.changli.e_while;

import java.util.Scanner;

public class Demo1While {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int i = sc.nextInt();
        int sum = 0;
        while(i>0){
            sum+=i;
            i--;
        }
        System.out.println(sum);
    }
}
